Not Applicable
Not Applicable
1. Field of the Invention
The present invention relates to a push-button switch and, in particular, to an overload-protection push-button switch with a retractable actuating mechanism, in which a rocker actuator having a retractable body is disabled in case of overload so as to accomplish an overload-protection. The switch needs to be manually reset after overload.
2. Description of the Related Art
There are many types of push-button switches for various applications, such as one having a turn-on indicating lamp and one providing an overload protection function. In terms of one having an overload protection function, there are also several kinds of protection principles or mechanisms being adopted. For example, both the blowout of a fuse wire and the thermal deformation of a bimetal blade have ever been adopted as a trigger source for an overload protection. However, the fuse wire is not repetitive and thus its utility rate gradually decreases. As for the thermal bimetal blade, there are many kinds of mechanism, such as those disclosed in U.S. Pat. Nos. 5,786,742, 5,223,813, 4,937,548, 4,661,667, 4,931,762, 5,451,729, and 4,704,594.
For example, in the U.S. Pat. No. 5,786,742, a so-called power-cutting member (72) used to alternatively set a set and a reset position of a switch is disclosed. In that case, a bimetallic blade (75) is used to push a shaft seat (71) to trip and automatically reset a switch However, the contacts in such a switch are directly depressed by a button. Thus, if the button has jammed or pushed down by an external force, it would be kept in its conducting position even if overload occurs. Moreover, such a switch is not economical because of a use of up to four contacts to construct a conducting circuit. It also increases the possibility of generating an arc. Furthermore, it is troublesome in assembly due to a need for connecting a wire between the bimetallic blade (75) and the conducting plate (74).
Is In U.S. Pat. No. 5,223,813, there are a bimetallic blade (13), a common trip (17) actuated by the bimetallic blade, and a cam member (27) which is incorporated with a rocker actuator (33) to make contact members (7,1) contact together or separate from each other. In such a patent, the common trip (17) will be displaced in response to a deformation of the bimetallic blade so that the cam member (27) is released and the switch trips. However, even though the common trip is indirectly actuated by a rocker actuator so that a jamming of the rocker actuator or a contact of the contact members by a neglectful re-push after overload can be avoided, such a switch is rather complicated. Moreover, since it needs a wire to connect its cantilever spring (5) and its bimetallic blade (13), its assembly is also troublesome. Furthermore, a fail-action is possible in case of overload since the bimetallic blade may be unable to simultaneously actuate both of the rocker actuator (33) and the common trip (17).
In a circuit breaker disclosed in U.S. Pat. No. 4,937,548, a thermal actuator (76) is used to displace a lock lever (62) upon deformation so as to release a bell crank lever operator (52). In this case, even a jamming of the actuator and a connection between the contacts upon a neglectful re-push on the switch after overload can be avoided; such an arrangement is difficult to install an indicator therein. Moreover, since two thermal actuators are forced against one biasing spring, a tilt of the two thermal actuators may happen.
In U.S. Pat. No. 4,661,667, a double-heart-shaped cain locking mechanism is used to obtain two locking-positions. However, such a switch has not an overload protection function and a status-indicating function.
A main object of the present invention is to provide an overload-protection push-button switch with a retractable actuating mechanism, which can make sure of a trip action in case of overload.
Another object of this invention is to provide an overload-protection push-button switch with a retractable actuating mechanism that occupies small space under a condition without increasing the complication and loading of the bimetallic blade.
To achieve the above objects of this invention, this invention provides an overload-protection push-button switch with a retractable actuating mechanism comprising
a housing;
a switching circuit installed in the housing and including a first terminal, a second terminal, a first conducting leaf and a bimetallic blade; the bimetallic blade having a movable closed end, being able to move to an overload position from a normal position in case of overload, and an open end formed with a first and a second legs for respectively connecting the first terminal and the first conducting leaf; the first conducting leaf being movable between a conduction position in which the second leg of the bimetallic blade is electrically connected to the second terminal and a broken position in which the second leg is disconnected from the second terminal; and
an actuating unit installed in the housing, including:
a slidable pressing stem to be actuated to one of a set and a reset positions;
a positioning unit including a cantilever and a heart-shaped stepping recess and being able to position the pressing stem in the set position when the pressing stem is pressed downward;
an enabling supporter provided on the housing;
a rocker actuator pivotally supported on the pressing stem, having a main body formed with a nose for abutting against the first conducting leaf, and a sub-body retractably coupling to the main body and formed with a toe portion to be supported by the enabling supporter, and an abutting portion to be pushed by the metallic blade;
an actuator-reseating member for abutting against the rocker actuator during the returning course of the pressing stem back to its reset position so that the toe portion can move into a position to be supported by the enabling supporter;
whereby the toe portion could be enabled by the enabling supporter and the nose can make the first conducting leaf be alternatively located in its conduction position and its broken position in response to the location of the pressing stem in the set position and in the reset position respectively when the bimetallic blade is in its normal position, and whereby the sub-body will retract so as to make the toe portion depart from the enabling supporter and to make the rocker actuator release the first conducting leaf into a broken position in case of overload.
By means of the above structure, since the conducting leaf is indirectly actuated, the switch can still exactly and transiently trip at the time overload occurs even if the stem jams. Moreover, since the trip action of the actuating mechanism is accomplished by the rocker actuator itself, the actuating mechanism will occupy a small space along with free of increasing the complication and loading of the bimetallic blade.